Are asymptomatic airway hyperresponsiveness and allergy risk factors for asthma? A longitudinal study.

Airway hyperresponsiveness (AHR) is a characteristic feature of asthma, but it is unclear whether asymptomatic AHR is associated with a higher risk of asthma. The present study assessed whether there is an association between asymptomatic AHR in adolescence and asthma in adulthood. The association between allergy and development of asthma was also investigated. A follow-up study of a general population cohort of adolescents was performed 14 yrs after baseline. Respiratory status was assessed at baseline in 1989 and at follow-up in 2003-2004 by a respiratory symptoms questionnaire, spirometry and histamine challenge. Allergy status was also assessed. The respiratory status of 199 subjects was assessed twice. In total, 91 (46%) subjects had the same AHR status in combination with respiratory symptoms at follow-up as at baseline. Adjusted for age, sex, allergy, family history of asthma and smoking history, having asymptomatic AHR was not significantly related to having asthma 14 yrs later (odds ratio (OR) 2.15, 95% confidence interval (CI) 0.67-6.83). For subjects with allergy at baseline, the OR for developing asthma was 4.45 (95% CI 1.46-13.54). Screening for asymptomatic airway hyperresponsiveness in adolescence does not identify subjects at risk of developing asthma. Conversely, the presence of allergy in adolescence does seem to be a risk factor for asthma development.